Protective device.



G. F. GRAY.

PROTECTIVE DEVICE.

APPLICATION FILED MAR. 1o. |913.

Patented Mar. 21, 1916.

Fig. l.

Inventor: Geo e F' rag S CDY-neg.

Witnesses;

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lUNTTED STATES PATENT OFFICE.

GEORGE -F. GRAY, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE.

Speciication of Letters Patent.

Patented Mar. 21, 1916.

Application tiled March 10, 1913. Serial No. 753,179.

T o all whom it may concern:

Be it known that I, GEORGE F. GRAY, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Protective Devices, ofwhich the following is a specification.

My invention relates to protective devices, and more particularly tothat type of device for use in the protection of low voltage'circuits.

The protection of low voltage apparatus from damage by lightning is animportant problem to engineers engaged in telephone, railway signal andsimilar' lines of work. Various kinds of protective devices have beeninstalled on low voltage lines but with apparently little success. Mostof the devices used have the disadvantage of grounding or shortcircuiting which in railway signal work is especially dangerous because,as is often the case, the grounding of such a circuit causes a falsesignal to be given. These devices furthermore are subject to such agreat maintenance expense that their use is to a great extentrestricted.

The object of my invention is to provide a protective device for useupon all low voltage circuits such as telephone, telegraph, railwaysignal. fire alarm, and similar circuits, which will be of economicaland durable construction, with low maintenance cost and capable ofdischarging lightning strokes without damage to itself and also freefrom any possibility of short circuiting. To this end I provide aprotective device of unit construction consisting of -a hollow metallictube especially adapted to maintain a vacuum or inert atmosphere. Themetallic tube itself forms one electrode for a spark gap, the otherelectrode being a metallic disk mounted within the tube. With thisconstruction a protective unit is provided, with a spark gap in a vacuumor in an inert atmosphere. The protective unit is so arranged that itcan be easily inserted in a spring socket member mounted upon aninsulating base thereby operatively connecting the protective unit intothe line to be protected. Y

The novel features which I believe to be characteristic of my inventionwill be defined in thegclaims appended hereto. The

features of construction and mode of operation will be understood byreference to the following description taken in connection with theaccompanying drawing in which Figure 1 is a front elevation, partly insection, of a protective device embodying the novel features of myinvention; Figs. 2, 3 and 4 are sectional views of various forms of theprotective unit shown in Fig. 1; Fig. 5 is a diagrammatic view ofconnections shown in Fig. 1; and Fig. 6 is a diagrammatic view ofanother electric circuit in which my protective unit is used.

Referring to the drawings, I provide a protective unit A, consisting ofa hollow drawn metal electrode 1. This electrode may be made in severalshapes and of any non-corrosive metal but in the preferred constructionthe electrode consists of a hollow tube made of brass. Extending throughand projecting outside the tubular electrode `1 is an electric conductorin the form of a metallic rod 2. This conductor' or rod 2 is suitablysupported within the tubular electrode 1 and insulated therefrom as willbe hereinafter more fully described. Within the tubular electrode 1 is acoperating metallic electrode 3 which may be of a variety of shapesV butpreferably in the form of a plate or disk. This plate or disk electrode3 is securely mounted concentrically within the tubular electrode 1, andupon one end of the conductor or rod 2, being in conductive relationtherewith. The plate or disk electrode 3 is preferably of a non-arcingmetal such as a bronze or a brass` and may have either a plain or aknurled edge. A metallic sleeve 4 preferably made of a non-arcing metalis securely mounted upon the inner surface of the tubular electrode 1.The sleeve 4 and the disk electrode 3 are separated from each other by aconcentric spark gap 5. As the metallic sleeve 4 is in conductiverelation with the-tubular electrode 1, it forms a non-arcing facing forthe electrode 1. The protective unit A therefore consists essentially oftwo non-arcing electrodes separated by a spark gap. The tubularelectrode is arranged to be evacuated or to contain an inert atmosphereso that the spark gap 5 will always be in an inert atmosphere which willcause it t0 break down under a f lower potential than an air gap. By theuse of the term inert atmosphere in this trode 1 and in so passing,

specification and in the claims appended hereto, I wish to broadlyinclude either an inert gas or a vacuum.

My object in using non-arcing electrodes is to adapt the protective unitA kto more fully protect a low voltage circuit from abnormal conditions,Isuch as lightning discharges, current rushes due to crossing with powercircuits, etc. Non-arcing electrodes separated by a spark gap in aninert atmosphere reduces the excessive arcing and offers a preventive tothe following of the line or dynamic ycurrent after a discharge takes:place.

The conductor or rod 2 is rigidly supported and well insulated from thetubular electrode 1 by a specific arrangement of insulating materials aswill be hereinafter described. As shown in Fig. 2 the conductoror rod 2is insulated and rigidly held by a bushing 6.. which may be made of anydurable insulating material such as porcelain, glass, etc. In theconstruction shown the bushing 6,l1 is made of glass and is cast uponthe conductor 2 and inclosed in a metallic casing 7. f

It was found in practice, in the type of construction shown in Fig. 2,that a discharge may under some conditions, pass from the conductor 2 tothe tubular elecchp off portions of the bushing 6a. To resistthistendency the type of construction as shown `in Fig. 3 was adopted.In Fig. 3 the bushing 6 is of an insulating non-chipping material, suchas porcelain. By non-chipping, I mean not liable to be continuallychipped offor pitted by spark discharges. In the construction shown inFig. 3, I further provide a metallic collar 8. which is mounted upon theconductor 2 directly below and in conductive relation with the diskelectrode 3. This collar 8 fits into a hollow circular projection9 ofthe insulating bushing 6b and is separated therefrom by a small space asshown in the figure- The small space between the collar 8 and the insideof the hollow projection 9 prevents any short circuiting of the collar 8and the tubular electrode 1. When the spark gap 5 breaks downcontinuously, metal is vaporized which subsequently deposits upon thesurface of the bushing 6b impairing its dielectric strength and offeringa conductive path from the tubular electrode 1 over the surface of thebushing. This conductive path is, however. interrupted by the smallspace shown, which is too narrow for the metallic vapor to penetrate andhence no'dep osition of metallic vapor takes place. This small space,therefore affords ample protection from short circuiting caused by thedepositionmf metallic vapor. The disk electrode -3 is brought into closeproximity with thc'top of the circular projection 9 which greatlyreduces the tendency of 'arcing bei insulating bushing 6 is of the sameshape and of the same material as the'bushing 6b of' Fig. 3 but thecollar 8 is longer than .in Fig. 3 `and the outer surface of thecircularprojection 9 has a metal facing or sleeve 10 preferably of vnon-arcingmaterial. This metallic facing 10 extends above the top of the hollowprojection 9 in such a way as to break up any arc which may form betweenthe conductor 2 and the tubular electrode 1 thus easily extinguishingit.

In Figs. `2, 3 and 4, below and adjacent to the insulating bushings 6,6,.,and 6b isa layer of insulating material 11 of high melting point.This material may be of a variety of well-known materials but what Iprefer to use is a mixture of resin and coal tar pitch which has amelting point about 125o C. Adjacent t9 insulating material 11 is alayer of another insulating material 12, which is of plastic nature, oflow solidifying point and of low`melting point. This material maylikewise be of a variety of materials but I prefer to use a vegetablepitch which has a melting point about 60 C. A pressed, board washer 13saturated With linseed oil is placed next to the insulating material 12and adjoining the Washer is another layer of insulating material 11. Theboard washer 13 is .placed between the insulating material 12 and thelast layer of insulating material 11 to prevent any mixing of the twoinsulating materials. The insulating materials are added in a fluidstate, and'unless the board washer is used, when the last layer ofinsulating material 11 is added, owing to its higher melting point, itmixes with the insulating material 12 which is undesirable. To suitablyfinish and close the tubular electrode, an insulating plug 14 is placedadjoining the last layer of insulating material 11. This plug may be ofany durable insulating material preferably porcelain, and is securelyheld in place by spinning in the usual manner.

The closingof the tubular electrode 1, in the manner shown, is a novelfeature of the applieants invention. The materials used and theirspecific arrangement secures a maximum eiiciency for the device. Thebushings 6 and 6b are especially constructed and made of anon-chipping`material which is at the same time a material which can be accuratelymolded and is usually strong and able to withstand the sudden changes oftemperature incident to arcing. The bush-` ings 6 and 6 are not dependedupon to preserve the inert atmosphere in the tubular electrode 1, butsuch atmosphere is preserved by the especially developedinsulatingmaterials 11 and 12 and the specific arrangement of them. Having theplastic insulating material 12 so located in the tubular electrode is ofmaterial advantage. This material is of sulicient adhesiveness to adheresecurely both to conductor 2 and the sides of the tubular electrode 1and is only slightly affected by temperature change. Any expansion orcontraction of the tubular electrode 1 due to normal temperature changeshas a tendency to cause the insulating material 11 to crack or draw awayfrom the side of the tubular electrode. In such a case the insulatingmaterial 12 is of suflicient plasticity to fill up any cracks orfissures which may occur and thus keep theinert atmosphere alwaysintact.

When the insulating plug 14 is secured in place, the tubular electrodeis ready to be evacuated or an inert atmosphere introduced. One end ofthe tubular electrode 1 contains a depression 15 in which there is asmall perforation 16 through which the tube is evacuated or the inertatmosphere introduced in any manner desired. The depression 15 ispartially filled with a fusible material 17 through which a small holeis bored to the perforation 16. When the tubular electrode 1 containsthe proper amount of inert atmosphere, the fusible material 17 isrendered sufficiently fluid to close the small hole bored in it. therebyclosing the perforation 16 and sealing and finishing the tubularelectrode 1. The fusible material 17 may be a. solder or any other lowmelting point alloy.

If a continued discharge takes place between the disk electrode 3 andthetubular electrode 1, the tubular electrode becomes heated and thefusible material 17 becomes sufficiently softened to flow through theperforation 16. In such a case there would be danger of the fusiblematerial coming in contact with the disk electrode 3 in such a way as tobridge the spark gap 5 and short circuit the tubular electrode 1 and thedisk electrode 3. To prevent this action from taking place, a metallicdiaphragm 18. is securely mounted Within the tubular electrode 1 beneaththe depression 15. To effectively eyacute the tubular electrode it isnecessary that the metallic diaphragm 18 be perforated. Theseperforations or apertures 19 are shown at the end of the protubcrances20. The diaphragm 18 is made with protuberances 20 containing apertures19 in such a way as to form a cup shaped receptacle 21 into which anyfusible material 17 will flow. This receptacle 21 is of sufficient sizeand the apertures 19 so situated that no fusible material 17 can passthrough the diaphragm 18, and tbe unit A is thus protected from anypossibility of short circuiting.

Having thus described in detail the construction of the protective unitA, I will now describe the means by which this unit is applied to thecircuits to be protected. The unit A consists essentially of the tubularelectrode 1 which forms the outer casing of the protective unit and adisk electrode 3 mounted therein and separated therefrom by a spark gapin an inert atmosphere. This unit is adapted to be removably positionedin a spring socket member 22, shown in Fig. 1, which is mounted upon aninsulating base 23 preferably of porcelain. In Fig. 1 there is shown twoprotective units A and A mounted in spring socket members 22 and 22a,respectively. The spring socket members 22 and 22a are both connected tothe same metallic plate 24 which in turn is connected to a groundingrterminal or binding post 25. Thus both tubular electrodes 1 and 1a areconnected to the terminal The coperating disk electrodes 3 and 3a whichterminate in conductors or rods 2 and 2a respectively, pass throughinsulated openings in the base 23 which are situated at the center ofthe base of the spring socket members 22 and 22a respectively. Theseconductors 2 and 2.i make contact with spring blades 26 and 26arespectively in which turn are connected to line connecting terminals orbinding posts 27 and 27a respectively.

One of the novel features of my invention is the adaptability of theprotective unit A to the circuit to be protected. This unit isconstructed so as to be easily inserted into the spring socket members22 or 22a Without interrupting working conditions upon the line. Shoulda unit be damaged in any way, it can be easily and quickly replacedwithout shutting down the line. In its construction, the unit is soarranged that the tubular electrode 1 and the conductor 2 which isconductiyely related to the disk electrode 3, are connectedsimultaneously into the circuit. By simultaneously, I mean that bothelectrodes are connected in the circuit by one motion, which is theinsertion of the unit in the spring socket member 22.

Fig. 1 shows the connections for the protectiye unit when used in lowvoltage circuits especially telephone circuits, and Fig. 5 showsdiagrammatically the connections shown in Fig. 1. Une side of the lineis connected to line connecting terminal 27 and through spring blade 26,to conductor 2 of the protective unit A. Discharge is then made throughspark gap 5 to tubular electrode 1 through spring socket member 22,metallic plate 24 to terminal 25 and thence to ground. The other side ofthe line is connected to line connecting terminal 27a through springplate 26a to conductor 2a of the protective unit A. Discharge from thisline is-through spark gap 5a to tubular electrode 1a and thence throughspring socket member 22a, metallic plate 24 to grounding terminal 25 andthence to ground.

the circuit to be protected, without departhvoltage circuits or on.circuits where there ingHfrom the scope of my invention.

he adaptabihty of my protective device for the protection of other lowvoltage c1rcuits such as telegraph, railway signal and fire alarmcircuits will be apparent to those skilled in the art without especiallyshowing ,or describing the connections for the same.

In low voltage circuits the spark gap 5 is sufficient to prevent itsbreaking down under the nor al volta e of the line. The device Jcan alsoe used or the protection of higher is a possibility of crossing withhigh potential circuits, by providing fuses in the line or by usingseveral of the protective units in series. As is shown diagrammaticallyin Fig. 6, choke coils or inductance can also be used in conjunctionwith the protective unit for the protection of circuits where unusualconditions of. service, especially in certain railway signal circuits,demand it.

T here are certain advantages inherent 'in ,V my protective device ofthe structure shown,

which can be enumerated as follows: First, the protective device iseconomical and of durable and simple construction. Secondly, the deviceis adapted for use upon all low voltage circuits irrespective of theirfuncl tion. Thirdly, the device protects the circuit from all abnormalconditions which may arise such as lightning discharge, current rushesdue to crossing with power circuits. etc., and with no possibility ofshort circuiting, and lastly, the'protective device is of unitconstruction, so that the unit can be easily and quicklyconnected' inthe line or in case of damage can be easily replaced by another unit, inall cases Without dis-- turbing the working conditions of the line.

My invention may be embodied in many other forms than that shown anddescribed and I therefore do not desire to be restricted to the preciseconstruction shown, but intend to cover by the appended claims allchanges and modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Let-ters Patent of theUnited States, is

1. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere, one end of said electrode havf.

ing a depressionJ containing a perforation, fuslble materlal 1n salddepresslon and coverlng said erforation, a coperating metallic electro emounted within said hollow fusible material in said depression andcovering said perforation, a perforated metallic diaphragm mounted`within said electrode beneath said depression, a coper ating metallicelectrode mounted within said hollow electrode and separated therefromby a spark gap, an electric conductor connected to said coperatingelectrode and extending outside said hollow electrode, and

meansfor rigidly supporting and insulating said conductor from saidhollow electrode. e

3. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere, one end of said hollow electrode havinga depression containing a perforation, fusible material in saiddepression and covering said perforation, a perforated metallicdiaphragm mounted within said 'hollow electrode directly beneath saiddepression, a'cc'perating metallic electrode mounted within said hollowelectrode and normally'- separated therefrom by a spark gap, an electricconductor connected to said coperating electrode extending outside saidhollow electrode and insulated therefrom,

i and means for preserving said inert atmosphere in said hollowelectrode.

/4. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere. a coperating metallic electrode mountedwithin said hollow electrode and separated therefrom bv a spark gap, anelectric conductor connected to said coperating` 'electrode andextending` outside said hollow electrode, an insulating bushing mountedwithin said hollow electrode and rigidly supporting said conductor, thetop surface of said bushing sloping upward from said hollow electrodeand from said conductor, and means adjacent said bushing forhermetically sealing said hollow electrode.

5. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere, one `end of said electrode having adepression containing a perforation,

fusible material in said depression and coverlng sald perforatlon, ametalllc cooperating electrode mounted within said hollow o electrode,means for preventing said fusible low metallic electrode containlng aninert atmosphere, one end of said electrode having a` depressioncontaining a perforation, fusible material in said depression andcovering said perforation, a metallic disk electrode mounted within saidhollow electrode and separated therefrom by a spark gap, means forpreventing said fusible material when fluid from short circuiting saiddisk electrode and said hollow electrode, an electric conductorconnected to said disk electrode' and extending outside said hollowelectrode, and means for insulating said conductor from said hollowelectrode and fo-r preserving said inert atmosphere in said hollowelectrode.

7. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere, one end of said electrode having adepression containing a perforation, fusible material in said depressionand covering said perforation, a disk electrode mounted within saidhollow electrode and separated therefrom by a spark gap, a perforatedmetallic diaphragm mounted within said hollow electrode beneath saiddepression, an electric conductor connected to said disk electrode andprojecting outside said hollow electrode, and means for insulating saidconductor from said hollow electrode and for preserving said inertatmosphere in said hollow electrode.

8. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere, a non-arcing metallic electrode mountedwithin said hollow electrode, a nonarcing metallic sleeve mounted withinsaid hollow electrode\ concentric with Said nonarcing electrode andnormally separated from said non-arcing electrode by a spark gap, anelectric conductor connected to said non-arcing electrode and extendingoutside said hollow electrode, and an insulating bushing mounted withinsaid hollow electrode and rigidly supporting said conductor the'topsurface of said bushing sloping upwar'd from said hollow electrode andfrom said conductor.

9. A protective device comprising, a hollow noncorrosive metallicelectrode containing an inert atmosphere, a coperating metallicelectrode mounted within said hollow electrode and separated therefromby a spark gap, an electric conductor connected to said cooperatingelectrode and extending outside said hollow electrode, an insulatingbushing mounted Within said hollow electrode and supporting saidconductor, alternate layers of high melting point and low melting pointinsulating material surrounding said conductor beneath and adjacent tosaid bushing, the top and bottom of said alternate layers being of saidhigh melting point material, and an. insulating plug adjacent to saidalternate layers of insulating material, -said plug closing the end ofsaid hollow member.

10. A protective device comprising, a tubular metallic electrodecontaining an inert atmosphere, a knurled metal electrode mounted withinsaid tubular electrode, a non-arcing metallic sleeve mounted within saidtubular.electrode and normally separated from said knurled electrode bya spark gap, an electric conductor connected to said knurled electrodeprojecting outside said tubular electrode and insulated therefrom, andmeans for preserving said inert atmosphere in said hollow electrode.

11. A protective device comprising, a tubular metallic electrodecontaining an inert atmosphere, one end of said electrode having adepression containing a perforation, fusible material in said depressioncovering said perforation, a metallic perforated diaphragm mountedwithin said tubular electrode beneath said depression, a metallic diskelectrode mounted Within said tubular electrode, a non-arcing metallicsleeve mounted within said tubular electrode concentric with said diskelectrode and normally separated from said disk electrode by a sparkgap, an electric conductor connected to said disk electrode extendingoutside said tubular electrode and insulated therefrom, and means forrigidly supporting said conductor and for preserving said inertatmosphere in said tubular electrode.

12. A protective device comprising, a tubular metallic electrodecontaining an inert atmosphere, one end of said electrode having adepression containing a small perforation, fusible material in saiddepression covering said perforation, a metallic diaphragm mountedwithin said tubular electrode beneath said depression, a plurality ofprotuberances upon said diaphragm each containing a small perforation, ametallic disk electrode mounted within said tubular electrode andseparated therefrom by a spark gap, an electric conductor connected tosaid disk electrode and projecting outside said tubular electrode, andmeans for insulating said conductor from said tubular electrode and forpreserving said inert atmosphere in said tubular electrode. y

13. A protective device comprising, a hollow metallic electrodecontaining an inert atmosphere, a metallic disk electrode mounted withinsaid hollow electrode and separated therefrom by a spark gap, anelectric conductor connected to said disk electrode and extendingoutside said hollow electrode, an insulating non-chipping bushingmounted within said hollow electrode, alternate layers of high meltingpoint and low melting point insulating material surrounding saidconductor beneath and adjacent to said bushing, a washer4 between thelast layer of said high melting point and `said low melting pointinsulating materials,

and an insulating plug adjacent to said alternate layers of insulatingmaterial and closing the end of said hollow electrode.

14. A protective device comprising, two electrodes normally separated bya spark gap in an inert atmosphere, one of said electrodes being ahollow member inclosin said inert atmosphere, lthe other of saielectrodes being a disk member mounted .within said hollow member, aground terminal for said hollow member, a line connecting terminal forsaid disk member, and means whereby said electrodes may besimultaneously connected to their respective terminals.

15. In a protective device, the combination with a protective unitcomprising a hollow electrode, a disk electrode mounted within saidhollow electrode and separated v therefrom by a spark gap, andaconductor connected to said disk electrode and extend- )and saidconductor to said spring blade simultaneously. l

16. In a protectivedevice, the combination with a protective unitcomprising a hollow electrode, a co erating electrode mounted withinsaid ho low electrode and separated therefrom by a spark gap, and aconductor connected to said coperating electrode and extending outsidesaid hollow electrode, of two terminals, a spring blade connected to oneof said terminals, anda spring socket member connected to the other ofsaid terminals, said protective unit being removably positioned 'in saidsocket member to connect said hollow electrode to said socket member andsaid conductor to said spring blade simultaneously.

In witness whereof, I have hereunto set my hand this 8th day of March,1913.

GEORGE F. GRAY. Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

